The present invention relates to an improvement to the invention described in U.S. Pat. No. 4,189,725.
The present invention, similar to the previous invention described in U.S. Pat. No. 4,189,725, is an apparatus and method for sensing and displaying a numerical value associated with a condition which requires the interconnection of a sensing device which can sense the condition and produce an electrical signal proportional to the sensed condition. The condition which the preferred embodiment of the present invention is intended to display is the percentage of oxygen in the environment surrounding the sensing device. However, the present invention can be used to sense any condition where a sensing device can produce an electrical signal proportional to the condition to be sensed.
The present invention differs from the invention described in U.S. Pat. No. 4,189,725 by adding an improved apparatus and method for calibrating which corrects for both offset and slope error conditions, and, by adding an improved apparatus and method for monitoring batteries to insure that the accuracy and reliability of present invention is not compromised because the batteries are wearing out.